This proposal is part of a collaborative effort between me and Dr. R. Berger at the University of California, Santa Cruz designed to elucidate the interrelationships between sleep and thermoregulation in humans and other mammals. Our objectives are 1) to investigate the phenomenological and functional homologies between sleep, shallow torpor, and hibernation, and (2) to describe and compare the characteristics of the CNS regulator of body temperature during sleep stages, torpor, and hibernation. The first objective will be achieved by a series of experiments on humans and other representative species in which simultaneous recordings will be made of EEG, EMG, metabolic rate, skin and deep body temperatures during sleep at ambient temperatures above, below and within the species' thermoneutral zones. Similar studies will be made during torpor and hibernation cycles. The second objective is the focal point of this part of our joint proposal and will be realized by direct measurements of pre-optic/hypothalamic and peripheral thermosensitivity during wakefulness, sleep stages, torpor, and hibernation. Animals will have water-perfused thermodes chronically implanted astraddle the preoptic nuclei and hypothalamus. POH temperature will be manipulated and thermoregulatory responses measured during wakefulness, slow-wave sleep, REM sleep, and torpor at thermoneutral temperatures. These experiments will reveal any adjustments occurring in the CNS thermoregulatory system during sleep stages and torpor. Changes in the integration of peripheral thermal information as a function of arousal state will be studied by manipulating local or whole-body skin temperatures and measuring thermoregulatory responses during wakefulness, slow-wave sleep, REM sleep, and torpor. These experiments will establish the functional relationships between thermoregulation and sleep and will provide the necessary foundation for interpreting metabolic and body temperature changes observed during sleep. These experiments will also yield insights into the evolution of sleep, torpor, and hibernation.